Trojan Boat Forum

I have the opportunity to score a pair of very low hour Merc 8.1s horizons (370 hp) for a good deal.

I am wondering if you guys have put these in your 10 meter express's and how they perform.

I currently have Marine Power 454 320hp TBI's and the boat is a complete and total gas guzzling sled! Im running 2.04:1 gears with 18x19 3 bladed no cupp.

I have done all the measurements and these engines will drop right in. I already have mint Borg Warner 5000 7* down angle tranni's to couple them up to.

A friend of mine found out the hard way that they are not completely "drop-in". Make sure you have enough clearance over the top under the deck hatch. He had to cut into the stringers, cut out the shaft tubes and glass new ones in so he could get the engines under the hatch. Measure, measure, then measure again!

Merc's are based on GM blocks, and the Marine Power's you currently have are (I believe) based on GM blocks as well. That's a plus, as it means sending units / gauges and most other wiring is already compatible. That's one of the typical re-power problems - switching from old school Chrysler blocks that most older Trojans have to Crusader's (GM based blocks) or Diesels usually also requires all instrumentation to be changed as well.

you might also want to check on all the electronics and sensors that 8.1's need injected gas engines need alot of them where as older stuff just used simple thunder bolt black boxes. And in your other post you said the bottom was dirty clean her up and she'll run better..

When we did the repower we initially were going to go with Crusader 8.1 engines ane almost did that.

Ours is an express cruiser and as such has a diffferent engine location than the mid cabin models. As I recall there was a vertical clearance issue that would require some modification.

The 8.1 engine is a good replacement for the 454 and will definately provide some level of increased power and economy.

The best economy we saw on ther 454's was .8 nmpg.

This was achieved by replacing an incorrect fuel metering rod found in one carburetor, removing the exhaust deflectors, increasing the size of the air intake spark arrestors and increasing the size of the trim tabs.

It should be noted that fully equipped and optioned out, these boats weigh far more than the published 12,000 dry weight.

Do your homework and make sure this engine will fit. You may need to change the mounts. The correct gear ratio and prop size is critical. Keep in mind with the mid cabin the shaft is closer to the hull. This puts a limitation on your diameter. Once you confirm that number, factor in the engine's power curve and the correct gear ratio will be determined.

RWS

O.K.

I just saw the pic of your 10 Meter.

NICE LOOKING BOAT!

You may be able to use the existing trans you have.

Does your build have a full liner in the engine room?

Is one of your current engines counter rotating?

Is one of the replacement engines also counter rotating?

You may only need to modify the air intake of the 8.1, if any mod is required at all.

There is one additional issue for you and that is the shafts.

When we ran the numbers on mine they were borderline acceptable (they are LONG) and we would have moved to aquamet 22 shafts to increase the safety margin. Probably not an issue, but I simply didn't want to take any chances.

Now would also be a great time to install an oil change system like a Reverso or similar unit.

Good Luck,

RWS