Mercury 402x 35ss

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Hi, does anyone have any info on the 402x 35ss ?
It does not seem to have had much use in the history of outboard racing with this motor, I read the in between class never got off its feet ? I would like to develop an 84'35hp for racing.
15" mid
Crossflow looper piston ported, high comp domes
Mild porting with clean up
Custom cowling and pan for reduced weight
Mercury single ram trim custom adapted
STD weight 73kg hoping for 60kg or less
Nose cone box with LWP.

I started putting together the midsection and removing unwanted parts from the engine.
Choke assembly, front support plate, rubber isolating mounts and the pull start ring from the flywheel. I'm wondering if I can also remove the outer flywheel inertia ring, or it needs to be on there for the flex plate to work properly?
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It would be great if anyone has any information on the Mercury 402x 35ss? Surely all the 44xs guys back in the day, may have some info about this class and motor? . This would be a great place to include this Mercury outboard's history on BRF

Originally I thought the motor was called a merc 402x 35ss.
However trying to find further pictures and information I found this picture that is a new style graphics with just 35ss. So perhaps the early 2 cyclinders were the 402x with the later model the 35ss.
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[QUOTE
Hi, does anyone have any info on the 402x 35ss ?
It does not seem to have had much use in the history of outboard racing with this motor, I read the in between class never got off its feet ? I would like to develop an 84'35hp for racing.
15" mid
Crossflow looper piston ported, high comp domes
Mild porting with clean up
Custom cowling and pan for reduced weight
Mercury single ram trim custom adapted
STD weight 73kg hoping for 60kg or less
Nose cone box with LWP.[/QUOTE]

Contact Seaway Marine in Washington State….Seaway Marine .com…… Ask for Dave Losvar.

If I'm not mistaken, a 402 XS is 1/3 of a 1500 XS. Check the bored and strong. I think there are quite a few 1500 XS parts around.

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Originally Posted by Ron Hill

If I'm not mistaken, a 402 XS is 1/3 of a 1500 XS. Check the bored and strong. I think there are quite a few 1500 XS parts around.

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Correct, the Mercury 402 or 35 is 2 cyclinders of the inline 6. Same bore and stroke, same block just remoulded to suit less cylinders. Same carbys, same pistons which means the high dome pistons can be used for higher compression
, as noted in my previous posts, with this plan I intend to travel.
From my research they were a standard fishing motor powerhead with no other race modifications. So what I'm about to do, not saying I will be the 1st, but certainly developing something unique.

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Originally Posted by ice_spy

Correct, the Mercury 402 or 35 is 2 cyclinders of the inline 6. Same bore and stroke, same block just remoulded to suit less cylinders. Same carbys, same pistons which means the high dome pistons can be used for higher compression
, as noted in my previous posts, with this plan I intend to travel.
From my research they were a standard fishing motor powerhead with no other race modifications. So what I'm about to do, not saying I will be the 1st, but certainly developing something unique.

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As above… Seaway Marine should have parts.

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Originally Posted by DeanFHobart

As above… Seaway Marine should have parts.

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Thanks, I already contacted Dave at Seaway, he has no knowledge on the engine.
I don't need parts, only wanted to know if anyway had played with this motor developing more HP from it, and any racing history it may have had. He suggested BRF . Lol

By the time the 402XS came out Mercury was moving away from the "Direct Charge: Pistons, and building V6 motor.

Most 402 XS's that I knew about broke the sleeves around the exhaust ports. We kind of surmised that the exhaust was getting out fast enough and the engine developed enough heat to crack the struts in the ports.

My dad being the engine builder that he was, noticed a drop in RPM when the engine warmed up. HE SPENT MANY HOURS RUNNING MY MOTOR IN OUR TEST TANK.

In the spring of 1977 I broke Kilo records in 35 SS Hydro and 35 SS Runabout. I out ran BOB WARTINGER'S TIME IN 35 S HYDRO.

The one thing we didn't know was that gapped plugs would run in a surface gap motor. Clark Maloof taught me that after he beat me at the 1977 National. I could beat him o the turn but my surface gap plug would load in the corners, and Clark would drive around me...

Replacement locks were expensive and didn't last very long. Most 402 XS's got switched to 55-H's or D Motors, a fishing blocks were made legal and powerheads were everywhere, cheap!

Thanks Ron, that gives me a bit of an idea about the days when this motor was being run. So the 35hp performance was ok ? Top mph ? Would it rev up quick enough out of the corners ? Or bog down and take time to reach top end ?
I read this motor suffered from the heavy flywheel ? Or was that the early 4 cylinder 402? Was the inertia problem only present on V hulls ?
It was quickly coined as a failure with Mercury as it was coming back with broken crankshafts, when loaded up low rpm ONLY. Apparently due to a lack of center bearing crankshaft support. The starter motor broke its brackets, and was resolved by fitting an extra lower strap clamp to the motor.
The exhaust port windows (3), look very small to me and could be a choke point for heat. I intend to port the exit casting alot. There is ways to reduce the temp on the exhaust side cylinder walls, I may have to incorporate this into the build.

So how did you make out with this build any follow up?, video?

Quote:

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Originally Posted by Ron Hill

By the time the 402XS came out Mercury was moving away from the "Direct Charge: Pistons, and building V6 motor.

Most 402 XS's that I knew about broke the sleeves around the exhaust ports. We kind of surmised that the exhaust was getting out fast enough and the engine developed enough heat to crack the struts in the ports.

My dad being the engine builder that he was, noticed a drop in RPM when the engine warmed up. HE SPENT MANY HOURS RUNNING MY MOTOR IN OUR TEST TANK.

In the spring of 1977 I broke Kilo records in 35 SS Hydro and 35 SS Runabout. I out ran BOB WARTINGER'S TIME IN 35 S HYDRO.

The one thing we didn't know was that gapped plugs would run in a surface gap motor. Clark Maloof taught me that after he beat me at the 1977 National. I could beat him o the turn but my surface gap plug would load in the corners, and Clark would drive around me...

Replacement locks were expensive and didn't last very long. Most 402 XS's got switched to 55-H's or D Motors, a fishing blocks were made legal and powerheads were everywhere, cheap!

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Also true with the Merc 25ss with surface gap plugs poor plug for racing. We racers quickly found the projecting center cold Champ L61Y gapped plug with cut back ground electrode (Champ made them that way) And with the CD ignition could gap at 0.050 and beyond and read them. I indexed them as well to the intake ports. This made a big difference with the 25ss in the circuit racing.

Quote:

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Originally Posted by ice_spy

It would be great if anyone has any information on the Mercury 402x 35ss? NFL crypto betting Surely all the 44xs guys back in the day, https://www.viberate.com/music-analytics/may have some info about this class and motor? . This would be a great place to include this Mercury outboard's history on BRF

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indeed looking for info on the Mercury 402x 35ss, especially from the 44xs folks. Sharing its history on BRF would be awesome!